Bridges are oldest conveying and transportation structure of world: and these constructions had very strategic duty through history Because of many problems; many of them have been destroyed annually. The most important reason for those structural failures is piers scouring. The general method for protecting those structure against scouring; are using some protecting methods such as ; using collar or rip rap around the pier ,but these ways are so expensive. A new method for achieving this goal is providing a specific space at bridge pier advisedly. In this situation; it could be possible that power of shoe scouring has been controlled effectively by increasing time of pier scouring operation. Beside flow which passed through Space between piers is able to govern pressure gradient at down side of pier location. At this research a new soft ware (Flow 3d software) (Multi dimension adaptable software of complex hydraulic circumstances) has been used in complete manner. This software is special model of computational flood dynamics Software (C.F.D), and it had been presented by flow Science Company. All equation at this model has been solved with finite volume method principles. For choosing the best geometric Space (gap) in bridge pier; many different shape with different length and width from bottom of bridge pier have been created first. Then flow dynamic condition around pier location has been investigated totally. Therefore: the best algorithm and shape have been chosen successfully by using bed shear stress measurement.